In an aircraft gas turbine (jet) engine, air is drawn into the front of the engine, compressed by a shaft-mounted compressor, and mixed with fuel. The mixture is burned, and the hot combustion gases are passed through a turbine mounted on the same shaft. The flow of combustion gas turns the turbine by impingement against an airfoil section of the turbine blades and vanes, which turns the shaft and provides power to the compressor and fan. In a more complex version of the gas turbine engine, the compressor and a high pressure turbine are mounted on one shaft, and the fan and low pressure turbine are mounted on a separate shaft. The hot exhaust gases flow from the back of the engine, driving it and the aircraft forward.
After a period of time in service, the tip of the turbine blade (called a “squealer tip”) is typically eroded, oxidized, and corroded by the impingement of the hot combustion gases. Because the gas turbine blade is expensive to produce, it is preferable to repair the damaged gas turbine blade rather than to discard it, if at all possible. The repair of the gas turbine blade tip is performed by grinding away the damaged material and replacing it with new material to define a repair squealer tip. The replacement is desirably performed by welding the repair squealer tip material to the tip of the airfoil, and then shaping the repair squealer tip material to the desired aerodynamic shape, typically by grinding.
The repair squealer tip material is preferably a nickel-base superalloy. In most cases the repair squealer tip material cannot be the same nickel-base superalloy as the airfoil because most airfoil materials are not readily weldable. Instead, other, more readily weldable superalloys are chosen. However, in certain cases such as where monocrystalline airfoils are being repaired, the selected repair squealer tip materials still are difficult to apply by welding, so that the yield of successful repairs is not as high as is desired.
There remains a need for a repair procedure for monocrystalline nickel-base superalloy gas turbine blade tip, which produces acceptable mechanical performance of the repair squealer tip and also is economic. The present invention fulfills this need, and further provides related advantages.